Engine



ENGINE 3 Sheets-Sheet 1 Filed March 24, 1948 INVENTOR v ATTORNEYS.

Oct. 14, 1952 Filed March 24, 1948 A. s. HERRESHOFF ENGINE 3Sheets-Sheet 2 ATTORNEYS.

1952 A. G. HERRESHOFF 2,613,651

ENGINE Filed March 24, 1948 3 Sheets-Sheet 3 4 INVENTOR ATTORNEYS.

Patented Oct. 14, 1952 UNI-TED STATES PATENT OFFICE ENGINE Alexander G.Herreshoif, Grosse Pointe, Mich, assig'nor to Ghrysler Corporation,Highland Park, Miclr.,acorporation of Delaware ApplicationMarch. 24,1948, Serial. No. 16,801

2Claimsi' I This. invention, relates primarily to internal combustionengines. of the, double acting'type.

Inthe. double acting tyne. o1) en ine a doub ended piston is employedfor reciprocatory movement in a working cylinder, such engines beingarranged to provide a. combustion. chamber at each. end of the cylinderfor cooperation w t each end of the. double ended piston. En in of this.general type are known. in he ar and employ a. crankshaft which is direcly operably QOnne-Qted the e. p ston without. the use Connect-ins rodof. the ore; conventional ype. of engine,

I is anobiect of my inventionto Provide: an ine havingvimprovedcompactness for av given Output h re y in. comparison with knowne gines of equivalentou put',an en ine constructed in accordance. withmyinvention occupies cm: siderably less space. Such anengine is.desirable formany uses a lior examplaior. driving motor vehicles whereinspace saving, aIQng with Weight and cost reduction, areconstantlystriven for,

Another object. is. to provide. an engine of improved; simplicity of;parts especially in connecion with. a. double actingtype of engine.

r er object. ofmy invention. is, to provide an improved double.actingengine. having its. parts so arranged as to provide improvedmechanical relationships or the p rts and at the. same time minimize.theoverall dimensions. of, the. engine for. an engine of aeiven'displacement;

Further objects of. my. invention.. in its more limited aspects are. toprovide a do 9 ac in engine of. improved compactness. in which. nowithstanding the necessity'ior. the crankshai extend. through the doublee ded pi tonlthe. piston rings do. not. overtravel the slots oropenings'in, the cylinder; hedouble ended. piston. is of. uniformdiameter as is the cylinder. in; which the piston slides the. pistonintermediate; body structure. Dloviding the ties between the pistonendshes entirely within the cylinder. bore; and the crank. as well asatl'eas thoseportions of the. bearing. block which are disposed immedi.-ately adiacent the piston slideway' are. sov arranged. as to at alltimes lie. within. the cylinder bore. In, addition, in order that the.optimum of compactness and'engine output-be. obtained, I preferablylocate the innermost. piston, ring. of each pistonheadof'tho double,piston as closely as practicable to.v the crankshaft and o the cylinderblock, openings for the crankshaf bearloss when. such piston head is inthe extreme limit of its strokingmovement inw rdly- In carrying out myvinvention, I have provided.

as,- a further object of my invention, a double acting engine ofrelatively large bore strolreratio which isv most desirable forcompactness while at the same time realizing all the other objects. ofmy invention. Heretofore, in engines of; this type, it has been deemednecessary to provide. a relatively small bore stroke ratio at asacrifice of compactness or to incorporatestructural'arrangements at'asacrifice'qf other desirable character'- istics. This isespecially so inconnection with engines dealing with conventional high gas explosi'onpressures. and while my invention is primarilydirected to such enginesit may also be of advantage in other machines. utilizing unusually highpressure operation in the ordjenof engine pressures rather than ordinarypressures usual-1y dealt; with in compressors, for example. However,generally speaking, compressor problems are quite. different from engineproblems andmany'arrangements. acceptable for compres sors would resultin failure if employedin modern engine structures or in other highpressure'machin Another object. is to provide a' double acting enginearranged for improved" installation in, a motor vehicle by reason of a,novel construction and. disposition of the cylinder block, valving,cylinder heads, and oil reservoir,

An additional obj ect is to provide. an improved and simplified assemblyof engine block, crankshaft, and camshaft components.

Yet, anotherobject is to provide an improved lubricant, drainag fr m thevalve chamber. abo the pistons, to theoil reservoir below'the pistons.

Further objects and advantages of my invention reside in thenovelcombination and arrange; ment, of parts, more particularlyhereinafterfset forth, reference. beingmade; to the accompanying dra ns; in which:

Fi 1 aions-itudinal sectional plan view through aportion. of the.engine; Fig. 2 isra transverse sectional elevational-view through atypical cylinder of the 1 engine;

Fig. 3 is a sectional view ofthe left hand-piston and slidehead orhearing block in their- Fig. 1 positions, the view'being takenasindicated by section line 3-3 of Fig. 1;

Fig. 4a is a transverse sectional view taken along line 4 4'ofFig. 3 butshowing the bearing block of the piston at the leftend of Fig, 1 injoneoffits; extreme positions of. mov m n la erally from th ositionof, Figs.1 and 3, portions of the camshaft being alsoshown;

Fig.5. is a diagrammatic view illustratingth 3 motion of the bearingblock relative to the piston;

Fig. 6 is a diagrammatic perspective view of the crankshaft.

In the drawings, reference character A represents the engine crankshaftstructure which, for reasons of assembly of the engine, is shown builtup in a generally conventional manner. This crankshaft structure has aplurality of sections 53 1 each composed of a central axial bearingportion l l, and offset crank-forming end portion B, and the diagonalportions 53 obliquely connecting each of the bearing portions with apair of the terminal crank portions 13. The sections Iii areappropriately connected in any well-known manner, as by fasteners Mwhich join a crank portion B with an oblique portion l3 of an adjacentsection if}, the engaged portions having matching serrations [5 tofacilitate the assembly and increase the efficiency of the joint.

'Each of the cranks B is embraced by a slide head structure or bearingblock structure C which has-a cylindrical bearing surface it having abearing fit with a crank B and a pair of diametrically disposed bearingsurfaces ll, [8 having a sliding fit in the slideway [9 of a doubleended piston D. This slideway extends transversely of the common pistonand cylinder axis [9 and the elements of the slideway bearing surface-s20, 2!

engaged by surfaces ll, [8 extend parallel with a plane2 which containsthe axis 2! of the crank B and which is perpendicular with the pistonaxis l9 the same being also true of the elements of surfaces [1, [8. Theslideway i9 is thus disposed perpendicular to a plane containing thepiston axis l9 and the axis 34 of the bearing portions 1 I of thecrankshaft structure A. The slideway l9 and bearing block C areimportant in that they provide suflicient area to take the high thrustsunder sliding action without developing undue wear and rattle. Thebearing block, as will be presently more apparent, presents criticalregions .at its corners or regions 22 which lie immediately adjacent theopposite extremities of the surfaces ,ll' and 18 in a directiontransversely of the piston axis, as viewed in Fig. 3.

The slideway I9 is carried by the struts 23 of the hollow double endedpiston D, each strut extending centrally inwardly from an associatedpressure-receiving head 24 of the piston, as shown in Figs. 1 and 3. Thestruts have marginal portions 25 extending inwardly beyond the slidewaybearing surfaces 29, 2| to retain the block C in proper position axiallyof the crank B. The piston D is of generally cylindrical formation andis provided with an inwardly extending annular skirt portion 26 at eachend. The heads 24 of the piston are tied or connected togetherstructurally as, for example, by an intermediate body structure 28. Thisintermediate body structure is pro vided with a pair of diametricallydisposed piston slots. or openings 21 extending axially of the piston.The slots 21 are so arranged as to provide unobstructed reciprocation ofthe piston and are of minimum length such that when the piston is at itsextreme limits of reciprocatory travel the respective ends of the slots21 are disposed with minimum practicable clearance with the crankshaftstructure in order to attain the maximum compactness for the engine.

Each of the skirt portions 28 is formed with a plurality ofring-receiving grooves opening outwardly toward the cylinder bore foraccommodating the desired number of outwardly expanding compressionrings, oil rings, and the like indicated at 29, the innermost ring beingdesignated at 30, the location of the latter being of materialsignificance in the more limited aspects of my invention, as will bepresently more apparent. Each ring is provided with a support land, thatfor the innermost ring being indicated at 3|.

The engine cylinder block structure E, according to my invention, isshown disposed such that the cylinders extend horizontally as shown inFig. 2, but in the broader aspects of my invention the axes of thepistons may extend vertically or the engine turned at any other desiredangle in which event the oil reservoir and certain accessories mayrequire re-orientation as will be readily understood. It will beunderstood that terms of reference to the horizontal and vertical areemployed only for convenience except as may be expressly otherwise setforth in the appended claims. Furthermore, my description will for themost part, be directed to a cylinder and piston assembly which istypical of the remaining cylinders and pistons of the engine. The blockE is formed in mating component half-portions 32, 33 having planar facecontact vertically at plane 34 which passes through the axis 34 ofcrankshaft structure A. The component portions 32, 33 are formed withcompanion cylinder bore portions 35 so that when the block portions arebrought together each piston D will be slidably contained in what ineffect is a single continuous uniform diameter cylinder F open at eachside of the block and made up of the two coaxial cylinder bore portions35, as shown in Fig. 2. The cylinder block portions are formed withpairs of mating or companion openings or recesses for receiving thebearing portions ll of the crankshaft structure as will presently bemore apparent. Thus the cylinder block portions together provide theopenings 35 for receiving the crankshaft structure. The cylinders F areclosed at each end thereof by a cylinder head G seated at the side ofthe portions 32, 33 of block E, each cylinder head having a plurality ofcombustion chambers 36 for the multi-cylinder engine illustrated. Eachcombustion chamber closes one end of a cylinder F and is provided withthe usual spark plug 31 where the engine is of the conventional sparkignition type.

The engine illustrated is of the four-stroke cycle type having acamshaft structure 38 extending longitudinally of the engine and drivenfrom one end of the crankshaft by gears 39, 40 in Fig. 4. The camshafthas its axis 40 in the plane 34 and is journalled in bearings 4| locatedat intervals above bearings I I and in suitable mating or companionopenings or recesses in the portions 32, 33 of block E. The camshaftoperates intake and exhaust valves 42 and 43 respectively, it beingunderstood that each combustion chamber 36 has an upwardly extendingvalve-receiving portion 44 accommodating the lift of a set of valves 42,43 for controlling the fuel mixture intake to the chamber 36 and thedischarge of exhaust gases therefrom as is well known for four strokecycle engines in general. Each of the component cylinder block portionsis provided with intake and exhaust valve seats 42 and 43 engaged by therespective valves 42 and 43.

The valves 42, 43 have their stems 45 extending toward camshaft 38 foroperation by camfollowers or tappets 46, a spring 41 yieldingly seatingeach valve and maintaining the tappets in contact with the various cams48 of the camshaft 38. The block portions 32, 33 are provided withintake and exhaust passageways 49, 50 extending from the seats 42*- andReef the respective intake and exhaust valves 42, 43 upwardly so as toopen at the upper faces. of block portions. 32, 33 for communicationwith conventional. intake and exhaust manifolds. (not shown).

For. an engine of the liquid-cooled type,.the cylinder heads G havecored chambers 5| for the circulation of a coolant, these chambersopening at 52 to the cored chambers 53 of the block portions 32, 33' forsurrounding the cylinders F with the coolant; The chambers 53 are opento. each other-for circulation of the coolant. at 54.

In order to prevent leakage of the coolant at the plane 34. where theblock portions 32, 33 are brought together in face contact, these faceportions are preferably lapped and coated prior to assembly with acommercial rubber cement or other suitable sealing medium which willpermit the block p'ortionsto be accurately fitted together to preservethe desired relationship in the component portions of the engineelements as, for example, the cylinders and the bearings for thecrankshaft and camshaft. The portions 32, 33 of the block E are heldtogether in assembled relationship, along with thecylinder heads G,crankshaft A. and camshaft 38', by a plurality of tie-bolts 54 whichextend laterally all the way through the component cylinder blockportions and through the cylinder heads G, the opposite headed ends ofthe tie-bolts being. seated on suitable faces provided by the outersides of the longitudinally extending cylinder heads G- In carrying outmy invention, I have provided certain physical relationships of thevarious parts in order to obtain maximum compactness of the engine whichis of the greatest practicable importance. In automotive, aircraft, oreven stationary power plant installations, engineers have striven toprovide an engine which will produce more power for a given physicalsize, the latter also necessarily including weight and cost. Inautomotive.installations such compactness in engine constructions is ofthe greatest importance in providing a minimum of space for the powerplant and a maximum of space for the passenger or load compartment. aswell as a maximum of space. for wheel suspensions, steering. mechanism,and other vehicle. equipment. This, of course, means that if suchvehicle is powered commensurate with. standard practice my engine wouldoccupy muchless. space and would be much lighter and less costly tomanufacture.

I:have discovered that there. are certain critical relationships ofcertain of the parts ofa double acting engine, these beinginterdependent on each other so that if they are brought togetheraccording to my teachings-then the desired compactness will result. Onthe other hand, if certain of the component relationships are notobserved, then this in turn requires such distortion of other of theinherent relationships that the advantages of my invention cannot berealized, at least not to the extent possible by such observance.

In an engine having conventional carburetor type of aspiration,pressures in the combustion diesel: engine practice pressures of 1200 p.s. i.

and even more are utilized. In constructing a double acting engine, itis important that the diameter H, of the crankshaft bearings. ll, shouldbe a minimum consistent with allowable stress, and bearing loads. Forenginesof the conven-. tional carburetor aspirator type, I havedetermined that by utilizing available commercial forged material forthe crankshaft structure, the ratio. of the cylinder bore J to Hshould'be inv excess of approximately 2.4, say 2.4 to 2.6. If the ratiois materialy higher, then excessive deflection and. loads are placed.von. the crankshaft leading to failures at bearings. II and at the,bearing block C, for example. If this ratio is materially lower, then His too large in. relation to J from a. standpoint of necessary strengthand, of moreimportance, such relationship exacts a magnified penalty onthe ultimate size, weight. and cost, of the engine for a given poweroutput. The general relationship of J in terms of H is as follows:

ems e) where K is the length of the bearing 1 l, L is the totalallowable stress, and M is'the applied pressure on the piston. For goodpractice, I have illustrated the bearings II as being of a length Kequal to half their diameter. As the allowable stress of the material isabout 20,000 p. s.. i. it will be found that the ratio of J "to II is2.4.. In time other materials may be discovered which will permit thisratio of approximately 2.5 to be increased which will be of advantage infollowing the teachings of my invention and in my reference herein tospecific values of such ratio, I, naturally contemplate such deviationstherefrom as may be made possible by the utilizing of materials for thecrankshaft which may be suitable. as well as deviations occasioned bythe use of combustionpressures higher than the assumed conventionalpressure of around 600 p. s. i. However, for modern practice as asubstitute for present popular automotive engines the ratio ofapproximately 2.5 is chosen as being determinative of achieving theimprovements set forth herein for purposes of illustrating my'invention.

With the values of J and H having been determined, the proper stroke ofthe engine is also determined thereby as will be presently apparent andis not to be taken as any arbitrary value according to my inventon. Idetermine the maximum proper engine stroke for the maximum ofcompactness as that value which will cause the bearing block C to travelin a path such that the. continuity of the cylinder F will not beinterrupted outwardly of the crankshaft axis 34* at a distance greaterthan the interruption necessarily required for accommodating thecrankshaft A whereby the innermost piston ring 30 will not travel overany such interruption in the cylinder wall. As it is generally desirableto provide the crankpin B with a diameter equal to H, and as the bearingblock C surrounds the crankpin, it will be apparent that the sweep ofthe corner regions 22 of block C present critical limitations to themaximum proper engine stroke. However, by providing an engine stroke ofapproximately 50% of the value of bore diameter J, it will be found thatmy requirements can be readily fulfilled.

The minimum length N as well as the width N of the bearing block 0 asseen in Fig. 3 should be, from the standpoint of practicalconsiderations, approximately 1.25 times that of the crankpin diameterII. By proportioning the ratio of thebore J to the stroke 0substantially 2 to 1, while providing adequate ties for the oppositepiston heads 24, then the travel of the advancing corner region 22 willdescribe an arcuate path P which, as seen in Fig. 5, will at all timeslie within the cylinder bore.

In Fig. 5, the-regions 22 are preferably curved at 56 in the directionof the thickness of block C concentrically with the cylinder so thatthey may swing closely to the cylinder with substantially minimumclearance and without breaking into the cylinder and thereby notpenalizing the maximum available stroke. Such clearance can, as apractical matter, be maintained as little as .025 times the diameter ofthe crank portion I2.

The travel of the extreme element of an advancing region 22 isillustrated by circular paths 5! and 53 for the respective points 59 and60 on such element. It will be noted that these arcs do not cut thecylinder. In similar manner the travel of two points BI, 62 lying in anelement L at the intermediate region 55 is shown by circular paths G3,54 respectively which likewise do not cut the cylinder and the end facesof the block C between the corner regions 22 are provided with theaforesaid curvature 55 concentric with the cylinder bore. Thus, in theengine illustrated, thecrank portion 13 and block C lie within thecylinder bore during operation of the engine, this being especiallydesirable in connection with the crank and the corner regions 22.

The offset of the crank portion B is of such amount in relationship withthe cylinder bore J, and the bearing block structure C and slideway I!)are so constructed and arranged, that the regions 22 always lie withinthe bore of cylinder F when, during operation of the engine, the regions22 are disposed outwardly axially of the bore from parallel planes 64and 64 ,These planes are perpendicular to the cylinder axis l9 and aretangent with the crankshaft-receiving openings 35 By maintaining suchrelationship, the regions 22 will move in such a path that they will notrequire interrupting the cylinder bore axially outwardly from theinterruption at 35 necessary to receive the crankshaft structure.Therefore, if the piston rings clear to openings 35 then they may bedisposed to move close to these openings and yet always slide onuninterrupted portions of the cylinder bore even though, at times, thecritical corner regions 22 of the bearing block structure C lie outsideof the parallel planes St and 64 In fact, in my arrangement, no part ofthe structure C or crank portion B cuts the cylinder bore outside ofthese parallel planes and this'arrangement permits the rings to bepositioned for close approach to the openings 35 and the realization ofmaximum compactness for the engine as a whole.

It will be noted that the offset of the crank portion B, whichdetermines the stroke 0, is of such a predetermined amount inrelationship .with the'diameter J of the cylinder bore F that,

during operation of the engine, each of the oblique portions I3 of thecrankshaft structure A will sweep a path adjacent the intermediate bodystructure 28 of piston D such that, when the piston is midway of itsstroke as shown in Fig. 4, such oblique portion will be disposed in adirection transversely of the piston axis [9 with substantially minimumclearance 65 with respect to a piston tie-portion or intermediate pistonbody structure 28 which lies between a piston opening 21 and one-end ofthe slideway l9 andwhich is disposed'at such time adjacent a planeperpendicular to the piston axis [9 containing the axis 34 of thecrankshaft structure. My reference to minimum clearance will be readilyunderstood as meaning the usual practical nominal minimum clearance foraccommodating necessary shop tolerance operations. In production it isusually desirable to assemble crankshafts as forged and withoutmachining except for the bearing and crank journals and where necessaryto connect the crankshaft sections. Where such a forged crankshaftstructure is employed, without machining the outer surfaces of theoblique portions l3, and where the piston D is not machined as to theseportions adjacent the region of minimum clearance at 65, this minimumclearance should be about oneeighth of an inch plus or minus usual shoptolerances in order to most fully realize the advantages of myinvention. Of course, if the crankshaft or piston is machined at theregion 65 then this minimum clearance may be somewhat lessened. Theopposite head portions 24 of the piston must, of course, be connectedtogether sufliciently to maintain the desired rigidity of the piston toinsure its proper operation and therefore adequate thickness of materialmust be imparted to the piston intermediate body structure 28. When thisis effected, certain of the important objects of my invention may berealized by providing the oblique crankshaft portions [3 disposed tomove with substantially minimum clearance with reference to the pistontie portions thus insuring the maximum piston stroke and the maximumcompactness for the engine.

In connection with the piston rings 29, 30 it will be noted that theyare so disposed, in relationship with the crankshaft-receiving openings35 as to always remain in engagement with portions of the cylinder borewhich are disposed outwardly of these openings in a direction axially ofthe bore during operation of the engine.

An important characteristic of my invention in its somewhat more limitedaspects resides in the disposition of the innermost piston ring 30 ofeach piston D for movement contiguous to the associated crankshaftbearings II and contiguous to the cylinder block openings 35 for suchbearings. By so locating these inner rings the length of the piston iskept to a minimum and, therefore, the width of the engine is minimizedalong with the optimum in compactness, low weight, and low cost.Furthermore, such ring location in a sense determines the maximum strokeof the piston as I deem it to be desirable to have the piston ringsalways engage the continuously cylindrical uninterrupted wall portionsof the cylinder bore F to avoid danger of the rings expanding intocylinder openings with consequent damage to the rings, lands, cylinders,and leakage past the rings. Therefore, the rings should not overlap anycylinder openings at least to such an extent as to give rise to tendencyof the rings to expand into any cylinder openings or to otherwise causeundesired wear of the cylinder and rings and jamming and breakage ofthese parts.

The innermost ring 30 associated with each piston head portion 24 hasits inner surface boundary, axially of the piston, disposed in aringsurface plane 64 which is normal to axis l9 and disposed as shown inFig. 1 when such piston ways lie within the cylinder bore when, duringoperation of the engine, such region 22 is disposed outwardly axially ofsaid bore from such planes 64.

The bearin block C is thus maintained of minimum length in the directionof slideway l9 such that the corner regions-22 remain. within thecylinder walls at all times." Inasmuch as openingsin the cylinder wallsare necessary to journal the crankshaft and inasmuch as I' have providedan arrangement which causes the piston rings to avoid overlapping suchjournal. openings, certain of the advantages derived therefrom wouldbe,at least to some extent, lost if the bearing'block. C wasarranged'fo'r such movement as to require an opening in the cylinderwall into which. the piston rings could expand withqdestructive results.1

Certain of my engines arranged in accordance with my invention provide abore stroke ratio J/O of 2, as aforesaid, with the desired good results.Obviously some latitude in the ratios set forth herein may be taken, andI have cited specific quantitative examples by way of illustrating thebasic principles of my invention and not by way of limitation as amatter of exact figures. Likewise such engines incorporate a ratio ofbore to crankshaft bearing diameter J/H of 2.5 and 2.6 and a ratio ofstroke to crankshaft bearing diameter O/I-I of approximately 1.25.

The relationship of O/I-I is derived from J J 5-2 and from which thusfurther illustrating the desired relationship of stroke 0 in terms ofcrankshaft bearing diameter H dependent on a common relationship whicheach has with the bore J.

Any suitable crankshaft throw arrangement may be provided such as theFig. 6 arrangement of cranks for the four cylinder engine illustrated.Cranks and '2 are in the same plane .but 180 from each other. Cranks 3and 4 are likewise in a common plane and 180 apart. These two planes arerelated 90 from each other. This four cylinder engine is, in effect, aneight cylinder engine as each of the four cylinders hereinbeforediscussed in detail provides two combustion chambers each having itspiston head for operating the crankshaft. Obviously any number ofcylinders may be used to construct an engine within the teachings of myinvention.

The split cylinder block E facilitates the assembly of my engine. Thebearing block C and pistons are assembled on crank portions which arethereafter connected at M, i5. Then the block sections 32, 33 arebrought together to contain the various parts shown in Fig. 2 and thetie bolts 54' secured in place.

The camshaft bearings 4| are formed in halves for assembly in the matingsemi-cylindrical openings 66 of the block portions 32, 33 whereby thecamshaft structure 38 is rotatably journalled at its journal portions67. Between the openings 66 the cylinder block structure E is providedwith component mating portions 68 providing cam chambers whichaccommodate rotation of cams 48, these chambers being open to each otherby passages formed by component semi-cylindrical openings 69 in thefaces of the block portions 32, 33. Each passage 69 extends in thedirection of I0 the-camshaft axis 46 and: is located adjacent a bearing4| as best shpwnl in Fig. 4. Lubricant is supplied to the various movinparts in any appropriate manner (not shown) and the lubricant tending tocollect in the cam chambers 68 drains through passages 69- thence to thefront of the engine and through a similar passage Ill and downward-1y inthe casing H which houses the camshaft drive gears 39, and thence intothe oil reservoir or sump provided by the pan 1-2. This oil pan isappropriately secured to the'under face of block structure E, when theengine is mounted as illustratedby fasteners 13.

In order to relieve the hollow portions of each piston structure .D oflubricating oil escaping from the main bearings I l and the bearingparts at the crank portions Band slideway C, the block portions 32, 33are provided with passages formed by the component matingsemicylindrical openings 14. Each of these' passages has its-lower endopen tothe pan I2 and its upper endopen to a-cylinder F in the plane 34so that-each passage provides drainage from one cylinder to the oil pan.It will be apparent that the upper ends of these passages 14 areprotected by the heads of each piston from exposure to the combustionchambers 36 or to the portions of the cylinders F which, durin operationof the engine, lie outwardly from the piston heads in the direction ofthe cylinderaxes 19 The power is taken from the rear end of thecrankshaft structure 38 in a manner conventional with engines ingeneral.

Engines of various desired capacities may be readily made following theteachings of my invention. Engines having cylinder bores larger thanthat illustrated will naturally develop more total pressure on thepiston with consequent increase in size of crankshaft end bearindimension H. This would have a tendency to limit the available strokeexcept for the necessary increase in crankshaft bearing diameter which,in turn, accommodates a stroke of substantially half the bore diameter.As fuels of higher octane rating become more available or withsupercharged fuel mixture or with diesel cycles, higher compressionratios may be used thus increasing the piston load for a given sizecylinder bore and requiring increase in size of crankshaft and dimensionH. This will have the tendency to somewhat shorten the available strokein relation to the bore and increase the ratio of J/O hereinbefore setforth. However, such ratio will still in the ultimate not greatly exceedthe ratio set forth herein and even in such instances the maximum incompactness may be readily obtained by following the teachings of myinvention.

Features of novelty not claimed but disclosed in my subject applicationare more fully disclosed and claimed in the copending applications ofJohn P. Butterfield, Serial Nos. 16,645, 16646, 16,648, 16,649, 16,650,filed March 24, 1948, and Patent No. 2,571,198.

I claim:

1. A double acting engine comprising a cylinder block with a piston boretherethrough, a crankshaft formed of interconnected sections journaledin said block and extending transversely of said bore intermediate theends thereof, said crankshaft having journal bearin portions at oppositesides of said bore extending at right angles to the axis of the pistonbore and a crank located within said bore between said journal bearingportions of such size and shape as to be continuously positioned withinsaid bore during crankshaft rotation, the diameter of the bore beingapproximately 2.5 times the diameter of the crankshaft bearing portions,a double ended piston mountel in said bore and pierced by saidcrankshaft intermediate the ends thereof, said piston having aninteriorly disposed slideway, a unitary bearing block rotatablyjournaled on the crank and slidably connected to the piston slideway,said piston slideway extending transversely of the piston at rightangles to the bore axis, said bearing block being of a lengthlongitudinally of the slideway of not less than 1.25 times the crankdiameter, said bearing block being shaped such that the sliding bearingsurfaces thereof remain continuously Within said bore during crankshaftrotation, and said crank being of such shape that the ratio of thediameter of the piston bore to the length of the piston stroke isapproximately 2 to 1.

2. The engine structure set forth in claim 1 wherein the opposite endsof the sliding bearing surfaces of the bearing block are convexly curvedto permit the bearing block to have the maximum stroke transversely ofthe piston while maintaining the sliding bearin surfaces continuouslywithin the cylinder bore during crankshaft rotation.

ALEXANDER G. HERRESHOFF.

12 REFERENCES CITED The following references are of record in the fileof this patent:

UNITED STATES PATENTS Number Name Date 545,502 Hennegin Sept. 3, 1895980,263 Holsman Jan. 3, 1911 1,018,532 Twombly Feb. 27, 1912 1,047,860Twombly Dec. 17, 1912 1,140,292 Sharpneck et al. May 18, 1915 1,254,281Salway Jan. 22, 1918 1,287,797 Tietzmann Dec. 17, 1918 1,473,602Brockway Nov. 6, 1923 1,578,228 Yearsley Mar. 23, 1926 1,710,721 BosmansApr. 30, 1929 2,170,099 Stubings Aug. 22, 1939 2,404,906 Heald July 30,1946 FOREIGN PATENTS Number Country Date 772,815 France Nov. '7, 1934

